sql.DB Context support

[arbarlow]

Hi there,

Love the idea behind Kallax and I'm happy to start contributing, I'm opening an issue first to discuss and can then PR if need be!

I'm wondering if there is/have been plans for Go's new sql.DB Context support?
golang/go#15123

I rely on this heavily for distributed tracing

[roobre]

Hello!

Thanks for your interest in kallax :D

Regarding the conext support, I'm not sure how is this related to kallax. Could you explain a little more about where this could be added and what usages it would have?

[arbarlow]

Sure,

It allows you to pass a context to sql.DB methods, so that you can hook into that for passing along whatever you need, be it distributed tracing information or a user token etc.

For example, this library allows for sending traces to Google or for logging. https://github.com/ExpansiveWorlds/instrumentedsql/blob/master/sql_example_test.go

And here is how we send traces to Zipkin, https://github.com/echo-health/opentracing-gorm/blob/master/otgorm.go

So, whilst you might want to supply context with every method, another way is to have a method to attach a context and get back a copy of the store of similar. Or work much like the store.Transaction method works currently in that provide a function, but that wouldn't be my personal preference.

[Azuka]

Hi, just wanted to see if you were considering supporting this. Ideally the hook interface methods would take in a context, although that would be a breaking change.

Edit: That'd only be an addition. I noticed you're using squirrel underneath for query generation, which has context support. allowing context to be passed in would bring in all the advantages of contexts such as deadline support. I understand this would possibly impact both the code generation as well as reorganization of internal methods to reduce duplication. Is there any way I can help?

[clintberry]

Beyond tracing and user tokens, it primarily supports timeouts which propagate to sql.DB. This means if you set a time limit on your request and it isn't going to make it, sql.DB will honor that and cancel the query so as to not waste anymore postgres resources on a query you don't want anymore.

[giautm]

Sure, I'm looking for this feature too.

[giautm]

Any ETA on this??? Go's Context released for a long time (a year ago), support context.Context brings a lot of benefits, such as cancel query, logging, analyst, and multi-tenant support.

[roobre]

Hello, thanks for your interest. For now, not in the near future, as I don't currently have the time need to implement and test new features. Pull requests are welcome though.

[giautm]

👍 , I need some help to know the architecture of this project. For a quick look, we will change Store implement, and generator to deliver this feature?

[roobre]

Changes would need to be non-breaking. Probably something like we have for running with proxies: A .WithContext() method on Store which would return a store (or ContextStore, if not compatible) using a context for their operations.

[giautm]

Thanks for the suggestion, squirrel.DBProxyContext doesn't support context yet (receivers: ExecContext, QueryContext...), so we will switch to an internal interface. Hừm...

// Store is a structure capable of retrieving records from a concrete table in
// the database.
type Store struct {
	db        squirrel.DBProxyContext
	runner    squirrel.DBProxyContext
	useCacher bool
	logger    LoggerFunc
}